The present invention relates to a resin composition of a hydrolyzed ethylene-vinyl acetate copolymer, and more particularly to a hydrolyzed ethylene-vinyl acetate copolymer composition which has improved impact resistance and flex crack resistance and is suitable for use of moldings.
The hydrolyzed ethylene-vinyl acetate copolymer is remarkably excellent in rigidity, hardness, abrasion resistance, antistatic property and cold resistance compared to other resins suitable for use of moldings. However, the hydrolyzed copolymer is insufficient in impact resistance and flex crack resistance.
In order to improve the impact resistance of the hydrolyzed ethylene-vinyl acetate copolymer, there have, hitherto, been, conducted a method in which a plasticizer such as buthylene glycol or dioctyl phthalate is added thereto, or a method in which an ethylene-vinyl acetate copolymer is blended therewith. However, the former has defects that the plasticizer bleeds on the surface of the molded article and the molded article is remarkably lowered in mechanical properties. Also, the latter has a defect that the obtained molded article has a film of ethylene-vinyl acetate copolymer on its surface so the appearance of the molded article is impared due to the poor compatibility between the hydrolyzed ethylene-vinyl acetate copolymer with the ethylene-vinyl acetate copolymer upon molding in a molten state, though the impact resistance is extremely improved. Particularly, when injection molding, the obtained molded article has flow marks on its surface, resulting in that the preferable gloss or luster peculiar to the hydrolyzed ethylene-vinyl acetate copolymer disappears, or when blending with a pigment to give the colored molded article, the floating of the pigment is caused, which is an obstacle to practical use.
In order to solve the above-mentioned conventional defects, Japanese Unexamined patent Publication No. 218352/1988 proposes to blend a polyester with the hydrolyzed ethylene-vinyl acetate copolymer, Japanese Examined Patent Publication No. 24277/1969 proposes to blend a polyamide with the hydrolyzed copolymer or Japanese Unexamined Patent Publication No. 139733/1985 or No. 161453/1985 proposes to blend a polyamide-polyether block copolymer with the hydrolyzed copolymer. However, in case of blending the hydrolyzed copolymer with the above-mentioned polymer, the physical properties of the hydrolyzed ethylene-vinyl acetate copolymer is insufficiently improved, since the compatibility between the hydrolyzed copolymer is not necessarily sufficient with the each above polymer.
An object of the invention is to provide a resin composition of a hydrolyzed ethylene-vinyl acetate copolymer, having improved impact resistance and flex crack resistance.
This and other objects of the present invention will become apparent from the description hereinafter.